Historically oxygen generation has been achieved by electrolysis of water, photolysis and chemical conversions. One method still in use today is the Pressure Swing Adsorption Cycles (“PSA”) as described in U.S. Pat. No. 2,944,627 which is herein incorporated by reference. In a PSA system oxygen is produced by the selective adsorption of nitrogen from a feed air stream. The PSA has at least one, often two adsorbent beds, which are designed to attract oxygen gases at low pressures and release the adsorbed oxygen at higher pressures. The PSA processes can be used to separate gases in a mixture because certain gases tend to be attracted to different solid surfaces more or less strongly than others.
Another oxygen generation process that uses some of the principals of the PSA process is called the Vacuum Swing Adsorption (VSA). In a “VSA” process, gases are separated using pressure but unlike the PSA process it is done at lower absolute pressures. Although these methods do work, they require multiple pressurized vessels and valve systems making portability difficult if not impossible. That is, these systems require valve operations either done automatically or by carefully calculated timing cycles controlled by a PLC. Accordingly, these systems are quite large and therefore prevent a patient from directly wearing oxygen-generating system as a portable system.
Over the years, improvements to the PSA and VSA systems were made such as in U.S. Pat. No. 3,313,091 incorporated herein by reference. While the earlier PSA and VSA systems used crossover valving and zeolite adsorbing material to produce a product high in oxygen purity, these systems were neither consistent nor simple. To maintain consistent oxygen product, U.S. Pat. No. 3,313,091 used a vacuum pump to draw part of the adsorbed termed “waste gases” from the vessel or bed being purged. These advancements over the earlier PSA and VSA systems however, required more complex electromechanical design additions including added phase controlling, e.g. gas entry, vacuuming re-pressurization and dumping to allow oxygen gas as a product of several cycles to transfer through and out to a user or patient did provide a higher yield. Nor did it compensate for the problems of associated with nitrogen loading to oxygen ratios, or electrostatic charge build up on the zeolite surface, clogging and preventing transfers and fouling.
The next advancement in oxygen filtration came in 1980 and was described in U.S. Pat. No. 4,222,750, which is herein incorporated by reference. In this patent the vessels or beds of adsorbing filtration materials cyclically underwent both periods of adsorption in which said vessel or bed received gas from a compressor then reabsorbed from the beds using a vacuum pump. As one can see, this improvement added even more equipment to the systems making it even less likely to be used as a portable system.
Therefore, what are needed are filters that can be used without electrostatic charge build up, nitrogen loading to oxygen adsorption ratios plugging, and that eliminate expensive and bulky pressurized chambers/valves and other large equipment that can generate sufficient amounts of oxygen to be used in a portable breathing device. That is a filer material that can be produce oxygen at a rate and concentration necessary to maintain breathing is a patient without pressurizing and depressurizing chambers and opening and closely complex valve systems. The present invention provides a filter material that overcomes the short comings of the prior art and can be used in a truly portable oxygen generating system capable of maintaining proper oxygen levels necessary for breathing by a patient. The present invention is discussed in the section below.